Abstract [en]

Phase change materials (PCMs) have long been studied as thermal energy storage media. However, the Swedish company, Exencotech AB, reaching beyond this usual scope of PCMs, has designed a system that uses PCMs as working medium to produce electricity from waste heat. To achieve high system energy efficiency, PCMs with low heats of fusion and large volume expansions are favored. Interestingly, this is the opposite of the desired properties of a PCM working in energy storage applications.

This work has aimed to find suitable alternative PCMs for Exencotech. After an intensive literature survey, eight candidates are identified from several PCM types. They are subjected to T-history test and volume expansion test in order to map out their volume expansion density chart. After analyzing the results from the tests, four most promising candidates with different melting temperatures, A, B, C, D, are finally proposed.

The results of the work show that A has the highest volume expansion density which is 0.97 cm

3/kJ. It is the most promising candidate found out of the many that were considered, that gives the highest energy efficiency for Exencotech, if they are able to find a suitable heat source and a heat sink.

(In order to keep some information confidential to the general public, certain names and values are coded in this report)